When the amount of gastrointestinal bleeding is less than 50 ml, the presence of blood in the stool is not visible to the naked eye and can only be detected by an occult blood test, which is called a positive fecal occult blood test (also known as occult blood or positive occult blood). When the stool contains only 5 ml or more of blood, the occult blood test can be positive. The degree of positivity, such as a small amount of blood, the positive reaction is weak; more blood, the positive reaction is strong. Positive is indicated by “+”, “++”, “++++”. Positive changes are commonly seen in active ulcer disease, stomach cancer, colon cancer, hookworm disease, etc. Personally, I suggest that if one stool is positive for occult blood, don’t rush yet, you can randomly perform stool occult blood test 3-4 times within 1 month thereafter. If it continues to be positive for more than 1 month or does not turn negative after treatment, the presence of gastric cancer or colon cancer should be suspected and further diagnosis should be confirmed. Those with vomiting blood and black stool should be hospitalized for examination and treatment, while those with positive fecal occult blood test alone can go to outpatient clinic for further examination to clarify the diagnosis before treatment.